Can I claim clothes given to charity that were my father’s who died in June 2018?

[Ashby]

Yes.

In most cases, the amount your can deduct is the lower of (1) the Fair Market Value of the item or (2) its "Basis".

The "Basis" of an item that you received as a Gift is usually the original purchase price by the person who bought it.

The "Basis" of an item you inherited is the Fair Market Value of the item on the day that person died.